Effect of Cool Immersion Bath on Metabolic Changes among Overweight Individuals: A Randomized Controlled Trial

Abstract

Background: The increasing prevalence of overweight is a major health concern because of its links to heart disease and metabolic disorders. There is growing interest in identifying non-pharmacological interventions for weight control. Aim: This study aimed to explore the impact of cool immersion baths on the metabolic health of overweight adults through metabolic adjustments and increased energy use associated with temperature regulation. Methods: In a randomised controlled trial, 60 participants aged 18 to 25 years with a BMI between 25.0 and 29.9 were divided into two groups of 30. For eight weeks, the intervention group underwent a 20-minute immersion bath at 18–26°C every other day, while the control group maintained their usual routine. Measurements were taken before and after the eight-week period, including body composition, anthropometric measurements, physiological parameters, and biochemical parameters, such as blood glucose levels. Results: After eight weeks of intervention, the study group demonstrated significant within-group reductions in systolic and diastolic blood pressure, respiratory rate, fasting and postprandial blood glucose, hip and waist circumference, waist–hip ratio, waist–height ratio, visceral fat, and subcutaneous fat percentage. In the adjusted between-group analysis, significant differences were observed for systolic blood pressure (p<0.001), diastolic blood pressure (p<0.001), respiratory rate (p<0.001), postprandial blood glucose (p<0.001), hip circumference (p=0.004), waist circumference (p<0.001), waist–hip ratio (p=0.001), and waist–height ratio (p=0.001). No statistically significant between-group differences were observed for fasting blood glucose, body weight, BMI, body fat percentage, visceral fat, subcutaneous fat percentage, weight without fat, or muscle mass. Conclusion: The present study suggests that an alternate-day cool immersion bath intervention may have beneficial effects on selected cardiovascular, respiratory, glycaemic, and anthropometric parameters in overweight individuals. However, further research with larger populations and assessment of additional markers is required to validate these clinical benefits.